Know Thy Tube Amp!

By Rod C. Venger

Whenever I acquire a new tube amp, I always pull the chassis and photograph the entire circuit chain, inn an overall sense but also in closeups of various sections. I use a high quality digital camera with a tripod and good lighting. I do a quick, overall study of the amp while the chassis is out, but later on I study the photos so that I fully understand what the signal path is, what’s in the signal path, where one channel begins, where it ends and another begins, where the signal from various sources is going to or coming from, as well as noting where any test points might be, etc. I also seek out information on bias voltage/amperage, power tube requirements, known mods and a host of other things. At the very least, you need to know the basics of your tube amp’s S/R loop’s specifications and placement, as this affects your entire signal chain. Always ascertain whether or not you’ve got at least one tube acting as a buffer for your input signal if you’re using a loop. An excessive output signal from an FX unit can blow out your power stage, but this danger is greatly lessened if you have one or two preamp tubes acting as fuses before the power stage. Preamp tubes are generally cheaper than power tubes and certainly cheaper than transformers! Knowing your amp will probably extend it’s lifespan and you’ll likely sound better too.

1 comment to Know Thy Tube Amp!

  • Will

    Why on earth would you need to do that? And with no..”Danger-High Voltage” Warning? What has looking inside your tube amp got to do with tone? I don’t think I have ever seen such a ludicrous suggestion on any guitar related forum….ever.Can a geek play the blues….seriously odd.

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